Re: [Public WebGL] Loading WebGLBuffer from an HTMLImageElement

[Kenneth Russell <kbr@google.com>]

On Tue, Apr 12, 2011 at 9:00 AM, Glenn Maynard <glenn@zewt.org> wrote:
>
> On Tue, Apr 12, 2011 at 4:45 AM, Vladimir Vukicevic <vladimir@pobox.com> wrote:
>> It's a bit roundabout, but you can:
>>
>> - Load the image as an image
>> - Draw it into an offscreen 2D <canvas> of the same size
>> - Use getImageData
>> - Use the returned ImageData's data buffer with buffer[Sub]Data
>>
>> Requires an extra step with the canvas drawing (and associated extra memory usage), but should be possible.
>
>> ----- Original Message -----
>>> It currently doesn't appear possible to load a WebGLBuffer from an
>>> image, to use an image as vertex data. I can't do this manually, by
>>> writing the image to a 2d Canvas and passing its ImageData to
>>> bufferData, due to same-origin restrictions.
>
> That's what I described here: it doesn't work, since getImageData
> isn't allowed for cross-origin images.  A direct API can deal properly
> with the cross-origin issues, in the same way texImage2D does.

Uploading an image to be used as vertex data is a hack. You'll only be
guaranteed lossless data transfer with PNGs. I don't think we would
want to add these entry points in the general case as they would
promote poor application development practices. Why do you not want to
download binary data?

A couple of corrections to your original email. I don't believe there
is a way to transfer a texture into a buffer object natively with
OpenGL ES 2.0 APIs, as glGetTexImage is not available. Second, some
WebGL implementations today do support floating point textures via the
OES_texture_float extension; see
http://www.khronos.org/registry/webgl/extensions/ .

-Ken

> --
> Glenn Maynard
> -----------------------------------------------------------
> You are currently subscribed to public_webgl@khronos.org.
> To unsubscribe, send an email to majordomo@khronos.org with
> the following command in the body of your email:
> unsubscribe public_webgl
> -----------------------------------------------------------
>
>

-----------------------------------------------------------
You are currently subscribed to public_webgl@khronos.org.
To unsubscribe, send an email to majordomo@khronos.org with
the following command in the body of your email:
unsubscribe public_webgl
-----------------------------------------------------------